Our web hosting package does all what you require, including
courier-maildrop, postfix, auth with TLS and so on. If you don't want to
use it, at least you can have a try and see the way our installer does.
Here are the links:

oooops...
really ugly, ugly errors on the demo-panel - and the errorlog should
be set to 0.

Well, that's the demo version which is not up-to-date, and this is not
fully working because it's a demo version... Have a try with our current
stable!